Elastic-fluid turbine.



G. G. CURTIS. ELASTIC FLUID TURBINE.

APPLICATION FILED 0012,1905.

Patented Mar. 3, 1914.

Inventor 'Witnesses:

Attorneys.

' UNITED h T OFFICE.

' CHARLES GORDON CURTIS, on NEW YORK, N. r, ASSIGNOR, BY MESNE ASSIGN- as to obtain the most efhcient result as re v the temperature of the steam any consider- MENTS, TO GENERAL ELECTRIC COMPANY, A CORPCRATION OF NEW YORK.

ELASTIG-FLUlD TURBINE.

1,089,115, Specification of Letters Patent. Patented lug 3, 1914 Continuation of application Serial No. 631,481, filed April 9, 1897. This application filed October 2, 1905.

Y Serial No. 280.995. I

To all whom it may concern: l boiler first throughthe super-heater. accord Be it known that I, CHARLES CURTIS, I ing to the usual custom, I cause it first to citizen of the United States, residing at pass through a portion of the turbine in New York city, in the county and State of. which it is expanded to a definite extent, New York, have invented a certain new and and a portion of its pressure and its intrinuseful Improvement in Elastic-Fluid Turl sic energy is converted into work. If we bincs, of which the following is a specifi-. assume a. case where the boiler pressure sav cation. is 150 pounds (by gage), and the turbine be The object I have in view is to provide operated condensing, the expansion taking means by which superheated steam may be place in any threestages, on the principle efl'ectively utilized in m improved comdescribed in my Patent'No. 566,969 above pound steam turbine, which is particularly referred to, and all stages developing equal described in Letters Patent numbered amounts of. work, the expansion in the first 566,967, 566,968 and 566,969, granted Sepstage will bring the pressure down to about tember'l, 1896, and to do this in such a way' twei;ty or twenty-five pounds (gage pressure The temperature of the steam at this pressure will be only about 265 F. as compared with a temperature of 365 F. at 150 pounds pressure-a drop of 100. At this tempera ture the superheating can be carried on with hot gases which are at a-much lower temperature, so that there is much less danger of burning out the superheater tubes, and the pressure is sofar reduced that the danger of explosion is greatly reduced. After passing through the first portion of thesteam turbine, the steam at the final pressure of this stage, which, in the case supposed is twenty or twenty-five pounds, is conducted through a suitable reheater, which is preferably operated by the waste boiler gases, and in this reheater as much heat may be added as is desired.

The amount of superheat applied to the steam may be sufficient to keep the steam dry during the entire subsequent expansion down to the exhaust, or it may be only sufficient to carryit dry through a part ofthe subsequent expansion, for example, through the second stage of a three stage expansion. It is desirable, however, in order to obtain an efficient result, to have a degree of superheat at least equal to any condensation during the expansion, for it not only increases the energy of the steam and the velocity with which it can be made to act upon the blades of the turbine, but it diminishes the frictionof flow of the fluid against the surfaces of the blades, and thereby reduces the lossof energy from this cause. Whatever quantity of heat may be added in this way, however, will have two effects. First, if there be any water in the steam coming 70 gards economy of steam, and with the most desirable and safe forms of appartus.

This application is a continuation of an application for patent filed by me April 9, 1897, Serial No. 631,481.

The ordinary method of superheating steam by conducting it directly from the boiler and at boiler pressure through a super-heater before admission to the engine is open to both practical and theoretical objections. The tubes or-shells constituting the superheater are necessarily subjected to quite a high temperature, in order to raise able amount above the temperature of saturation at the given boiler pressure, and the apparatus being under considerable pressure," which becomes very large in the case of high boiler pressures, there is great danger of burning out or bursting. Moreover, superheating carried on in this way cannot be effectively worked with the waste gases from the boiler, owing to their low temperature, and hence an independent firing is required. v

My objectis to provide means whereby my improved steam turbine may be adapted to the use of superheated steam so as to secure the highest economy of steam, and und er such conditions that the superheating operation or operationsv are carried on at very low pressures and comparatively low temperatures, so that both the temperature and pressure to which the superheater is subjected shall be below the objectionable points, and the superheater may be operated with the waste gases from the boiler. I Instead of passing the steam from the ture of the steam,

' casioned by the superheat and at the same therefore, that in delivering 5 superheating to steam is dry and therefore free from the particles of water which in the case of saturated steam are being developed by condensation and deposited on the surface of the buckets, causing increased friction, it being borne in mind that the greater the any point, the

over from the previous expansion stage, as there will be unless the steam in the previous stage has been suificiently superheated in some way to prevent condensation during expansion, the first effect will be to reevaporate the water or'condensed portion, increasing the volume of the fluid to this extent; and, second, to raise the temperathus increasing its volume from this cause, and also increasing the intrinsic energy contained in the steam. After passing through the rehea ter, therefore, the volume of steam has been increased a definite amount, depending upon the amount of moisture in the steam as 1t enters the rethe rise of temperature ocfrictional retardation at greater cross-section of passage 1s, of course,

both of these causes, therefore, of cross-section or the the steam passageway, to give an efficient result, should be considerably less in the case of superheated steam than in that of saturated steam, and it is highly important that this ratio should be no more than that exactly sufficient under the existing conditions, for if the passageway be too largeat any point, the velocity may be only slightly less than it should be, but, nevertheless, theloss of ener may be considerable, because the energy de or work done increases "and diminishes with the square of the velocity! Hence, a very slightloss of velocity causes a much greater loss in efliciency. The proper theoretical ratio of expansion to provide for the correct conversion of pressure into velocity working with superheated steam is, -0 course, capable of calculation, but, to make provision for the efl'e'cts of friction and other causes affecting the flow, the proper ratio of expansion as well as the actual cross-section of passageway necessary to convey the. fluid should, in each case, be found by trial, depending as it does upon a number of conditions. This can best be done by making the passageway or parts of the passageway. in each part ofthe" turbine capable of-a double adjustment, as I have describedin my atent 589,466, dated September 7, 1897 so t at not only may the cross'section or size of the passageway be varied, but the ratio of expansion (in the nozzle at least) may also be varied and best adapted to the particular condition found to exist at each stage in the expansion. The apparatus may be so constructedas to provide this diminished' increase of cross section'either in the p 1.s p 1.s; 4 nozzle .itself or in the subsequent parts of the working passage,-or in both combined,-the desideratum being that the expansion finally determined upon'should be exactly sufiicient and no more than sufficient to develop the maximum veiocities at the points of action in the turbine so as to get the benefit, as far as possible, of the additional energy represented. by the superheat. The most satisfactory way of doing this is by trying different degrees of expansion under the particular conditions under w the turbine is to work in practice, until the best degree of expansion is found, and the most simple means of trying different ratios of expansion is to construct the nozzle, as

From one or the necessary increase ratio of expanslon in time its intrinsic energy or capacityto de velop velocity and 412's viva by proper expansion has also been increased. I have found, the steam after the next portion of my improved turbine, the expansion passage through which the steam is made to flow and .in which its velocity or energy is converted into work in the turbine in the next stage must be so designed as to provide for this increased volume of fluid, and must be also so designed as to provide the proper ratio or degree of expansion in the working passage (as described particularly in my Patent Number 566,968), so as to convert the pressure most effectively into velocity by expansion, and obtain the greatest sum total of velocities at the various points of action upon the moving parts of the turbine. The increase of cross-section or ratio of expansion in each portion of the turbine, including the nozzle, must, in order to et efiicient results, be somewhat less, in t e case of superheated steam or other elastic fluid than in the case of ordinary saturated steam; first, because the increase of volume by a given declinein pressureis less compared with the. velocity developed in the case of superheatedsteam than in the case of sat urated steam (the expansion curve in case of superheated steam being represented by the equation whereas the expansion curve of saturated steam 1s according to the equation 1357 1.11 PVnn and hence a less increase of cross-section in the expansion steam passages is required to develop the maximum velocityof flow than if the steam were saturated during expansion; and, second,because the diminution in the jets velocity by frictional retardation or surface friction, against the walls of the vanes and other parts of the passage may be considerably lessthan in the case of saturated steam, owing to the fact that the.

necessary to convey the given volume of fluid.

veloped described in my patent 589,466, so that itsratio of expansion may be increased or diminished, and at the same time the virtualvcross-section of the passage may be kept constant or maintained of sufficient size to transmit the quantity of steam received from the previousstage, and at the increased volume resulting from the subsequent revaporation and superheating. By trying different degrees of expansion, either by varying the nozzle or other parts of the working passage, and at the same time keeping the crosssect-ion of the steampassage in the two or more stages adjusted relatively to each otherof theturbine, the pressure and temperature will have become still further reduced. In

the case proposed, that of a three-stage ex pansion, the pressure at this point will be,

about 12 or 14 inches of vacuum, and the temperature, provided the superheat has been exhausted by the previous expansion so that the steam is then satuated, will be only about 163 F. The steam may then be passed through a second reheater, vwherein any condensed portion will be evaporated and the temperature of the steam afterward raised to the desired degree, its volume and intrinsic energy being increasedto a certaindegree, as before.

The third portion of the turbine I con-H struct similarly, so that the working passage through which the steam flows is adapted to carry the steam received from the previous stage, but at the increased volume, and so as to provide the expansion necessary to convert this superheated steam into work in this stage in the most efficient manner. Instead of passing the steam through the second reheaterythis may be dispensed with, and all the heat furnished to the steam by the first reheater, but theoretically it is preferable to divide the super-heating into stages, because in this way part of the superheating is carried on at a lower temperature than if all the superheating were done at once, and hence hot gases can be used to effect part of the superheating which are at a very much lower temperature, and the heat more readily transferred to the steam, the hot gases coming into contact with the reheaters in the order of the decline in pressure and temperature. The boiler steam may, of course, be superheated by a special superheater before it enters the first portion of the turbine, but 'I prefer either to dis-' pense with superheating entirely in the first or early'stages or to obtain a certain amount of superheating by passing the steam on its way to the turbine through a reducing valve, using a boiler pressure considerably above the pressure at which the steam enters the turbine. In this way the pressure may be reduced and the steam superheated to a certain extent by fwire drawing through the reducing valve in the well knownway, and a sufficient degree of superheat may practically be obtained in this way to keep the steam dry during the first or early stages of its expansion, and thus materially -increase its efficiency. I

While the use of steam as the elastic fluid has been so far particularly. referred to, I Wish it understood that m present invention is applicable toelastic fluid turbines employing other elastic fluids than steam.

he accompanying drawing illustrates an apparatus embodying my invention.

A, B and C represent the three sections cordance with my ratent No. 566,969, and operating, as does the turbine of that patent,

to convertand utilize in successive o era- 7 tions or stages, different portions of the pressure of the elastic fluid into 'vis vim. Each section of the turbine is, as described in said patent, inclosed in a separate fluidtight'shell, and is provided with an expan-I sion nozzle for converting the desired amount of pressure into m's who, and with an expansion working passage through movable varies, the passageway including the expansion nozzle and expansion working pas-- sage of each successlve section of the turbine being sufiiciently larger than the passageway of the preceding section to accommodate the increased volume of the fluid jet due to its lower. pressure, all as'described in said atent. The pasageway through each. of t e several sections of the turbine,

when used with superheated steam in accordance with my present invention, is, however, given proportions diiferent from those employed when saturated steam is used, as has already been described.

D is the steam boiler, and Eand F are reheaters located so as to be heated by the waste products of combustion from the boiler furnace.

G is the pipe conveying the steam'to the first section of the turbine; H and I are the pipes connecting the reheater E between the sections A and B of the turbine; J and K are the pipes connecting the reheater F betweenthe sections B and C of the turbine;

and L is the final exhaust from the section C of the turbine, which, in case the engine is operating as a condensing engine, will be connected with a condenser or other means for producing less than atmospheric pressure."

M is a reducing valve for wire drawing the steam before it enters the first section of theturbine, and N is a chamber located be- 85 of an elastic fluid turbine constructed in aca such stage being of greater tween the reducing valve M and the firstsection of the turbine.

Having now described my invention what I claim as new and desire to secure by Letters Patent is:

1. In an elastic fluid turbine, the combination with a turbine having a plurality of stages, means for withdrawing steam from a stage into a reneater, means for returning the reheated steam into ,a subsequent stage, area than the area required for saturated steam, but with the increase of ratio of expansion less than.

that required for saturated steam.

2. In an elastic fluid turbine, the combination with a, turbinehaving a plurality of steam fromv one stage into a reheater,

I tion with a turbine stages, each comprisinga nozzle and a rotor,

' the nozzles in the several stages being proanother to pass equal means ,for withdrawing and means for returning the-reheated, steam into a, subsequent stage, such stage being. of greater area than the area required for saturated steam, v

3. In an elastic portioned one to amounts of energy,

fluid turbine, the combinas stages, each comprising a nozzle and a workmg passage, means for -w1thdraw1ng steam and conveying it to having a plurality of;

from a stage into a reheater, means for returning the reheated steam into a subsequent stage, the working passage of such stage being of greater area than that requiredfor saturated steam, but with the increase of urated steam. I

This specification signed and witnessed this 28th day of September, 1905.

- CHARLES GORDON CURTIS.

Witnesses k. V t v LEONARD H.3DYER, JAB. F. COLEMAN.

and with its co-' operating working passage having a ratio of. expansion less than that required for sat- 

